Date: Mon, 22 Jan 2024 14:23:37 +0100 From: Baptiste Daroussin <bapt@freebsd.org> To: Mike Karels <karels@freebsd.org> Cc: Alexey Dokuchaev <danfe@freebsd.org>, Jessica Clarke <jrtc27@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: Re: git: 636592343c3e - main - tmpfs: increase memory reserve to a percent of available memory + swap Message-ID: <nfj3olj7diwjgcvea4tj323cye6bbwifdrodvpfv5xlkhrglh6@2h75aaihryp4> In-Reply-To: <04794665-EFCA-4E89-9956-B18684898C9D@freebsd.org> References: <202312191534.3BJFY3fo030908@gitrepo.freebsd.org> <FCB7B75C-1816-4F93-9560-59208F5A8781@freebsd.org> <Za3ldgmM-nbPNdxe@FreeBSD.org> <04794665-EFCA-4E89-9956-B18684898C9D@freebsd.org>
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On Mon, Jan 22, 2024 at 07:15:22AM -0600, Mike Karels wrote: > On 21 Jan 2024, at 21:48, Alexey Dokuchaev wrote: > > > On Mon, Jan 22, 2024 at 03:27:57AM +0000, Jessica Clarke wrote: > >> On 19 Dec 2023, at 15:34, Mike Karels <karels@FreeBSD.org> wrote: > >>> commit 636592343c3ec0feb61a4d8043676381384420dd > >>> > >>> tmpfs: increase memory reserve to a percent of available memory + swap > >>> > >>> [...] > >>> > >>> Add sysctl for vfs.tmpfs.memory_percent and the pre-existing > >>> vfs.tmpfs.memory_reserved to tmpfs(5). > >>> > >>> PR: 275436 > >>> MFC after: 1 month > >>> Reviewed by: rgrimes > >>> Differential Revision: https://reviews.freebsd.org/D43011 > >> > >> I just got: > >> > >> make[6]: Could not create temporary file /tmp/makeDl4i9S: > >> No space left on device > >> > >> after doing a buildworld -j4 on a 4 core, 16 GiB system where /tmp is a > >> tmpfs, with the prior buildworld having taken me past this commit, > >> which I strongly suspect to be the cause. Whilst I understand the > >> motivation behind your commits, this is a sad regression to have; it's > >> not exactly a particularly strange situation. > > Bug 276402 is about the interaction of this change with ZFS ARC, which > seems to be problematical. I spent some time investigating yesterday. > Depending on the dynamics, I get different results. If tmpfs grows, > the ARC will be reduced if needed. But if the ARC grows to the point > that tmpfs sets free space to 0 or quite low, attempts to write to > tmpfs fail without any reduction in ARC. > > Jess, two quesions: > > 1. Are you using ZFS on this system? > > 2. Can you try with vfs.tmpfs.memory_percent set to 100? > > > FWIW, I've seen two people complain about this last week, apparently > > this kernel OOM protection doesn't work very well. :-/ > > So far, I have only seen OOM kills when memory + swap are quite short, > with a tmpfs memory_percent above 95. But with ZFS, it can happen > when the ARC could have been reduced. > > I will investigate more today. If I don't find a way to resolve this, > I'll probably commit a change to set vfs.tmpfs.memory_percent to 100 > by default, at least for now, and if that works around the problem. > This is easily reproducible with poudriere, if you try to build some ports/packages which are big memory consumers, for example any chrome variant or just lang/rust, I have a machine with 64G of ram and it is impossible to get lang/rust build in poudriere (USE_TMPFS=all) without setting vfs.tmpfs.memory_percent to 100. the poudriere dies with plenty of no space left on device. Best regards, Bapt
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